1982 Urakawa earthquake
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| UTC time | 1982-03-21 02:32:07 |
|---|---|
| ISC event | 602579 |
| USGS-ANSS | ComCat |
| Local date | March 21, 1982 |
| Local time | 11:32 |
| Magnitude | 6.7–6.8 Ms[1][2] 6.9 Mw[3] 7.1 MJMA |
| Depth | 44.0 km (27.3 mi) |
| Epicenter | 42°09′29″N 142°21′40″E / 42.158°N 142.361°E |
| Areas affected | Japan |
| Total damage | $1 million USD[4] |
| Max. intensity | JMA 6− MMI X (Extreme)[4] |
| Tsunami | 1.3 m (4.3 ft)[4] |
| Foreshocks | Yes |
| Aftershocks | Yes, largest Mw 5.9[5] |
| Casualties | 167 injured[4] |
The 1982 Urakawa earthquake (Japanese: 浦河沖地震[6]) was a Mw 6.9 earthquake that struck off the coast of Urakawa, Japan, on 11:32 (JST), March 21, 1982.[7][8][9] The epicenter was 42°06′N 142°36′E / 42.1°N 142.6°E.[10] The earthquake was the largest earthquake in the history of the region. The earthquake caused 167 injuries and damage in Tomakomai and Sapporo.[11][12]
Hokkaido is situated on the Okhotsk Plate in between two main zones of seismicity. To the west, there is a convergent plate boundary with the Amurian Plate.[13] To the east, there exists a subduction zone where the Pacific Plate subducts underneath the Okhotsk. This is accommodated by slip along the Kuril-Kamchatka Trench and the Japan Trench.[14] This earthquake struck as the result of thrust faulting in an area of compression known as the Hidaka Collision Zone.[15] The same tectonic process, caused by the collision between the Eurasian Plate and the Kuril fore-arc uplifts the Hidaka Mountains.[15]
Earthquake
At 2:32 UTC or 11:32 local time on 21 March, a large earthquake struck off the shore of southern Hokkaido. The Mw 6.9 earthquake caused shaking that reached a maximum Japan Meteorological Agency seismic intensity scale Shindo of 6- and a Modified Mercalli intensity (MMI) of X (Extreme). The event struck at a depth of 44.0 km (27.3 mi), and ruptured along the Hidaka Collision Zone.[15] Inferred rupture dimensions were 12 km (7.5 mi) by 22 km (14 mi) with an average slip of 2.5 m (8 ft 2 in).[5] Aftershocks covered an area of 35 km (22 mi) by 25 km (16 mi).[9]
